It is known that the capsular polysaccharide K5 isolated from a E.coli strain (herein below simply called “K5”) described by W. F. Vann et al. (1981) in Eur. J. Biochem. 116, 359–364, shows the same sequence as the biosynthetic precursor of heparin and heparan sulfate (N-acetylheparosan) and is chemically constituted by repetitive disaccharide units formed by D-glucuronic acid and N-acetylglucosamine linked α1–4, while the disaccharide units d-glucuronyl-N-acetylglucosamine are linked β 1–4. The only difference, which is not important for the biological activities of the K5 and its derivatives, between the heparin precursor N-acetylheparosan and K5 polysaccharide, is the presence of a double bond in position 4(5) at the non reducing end of some chains of the polymer, as for instance described in EP 489647 and EP 544592 herein below mentioned.
After this first publication, other papers and patent applications described the preparation of the E.coli K5 polysaccharide having molecular weight ranges from few thousand to many hundred thousand Daltons. For example EP 333243, IT 1230785, EP 489647, EP 544592, WO 92/17507, WO 102597, and the paper of M. Manzoni et al. (1996), Journal Bioactive Compatible Polymers, 11, 301–311 are indicated.